Programming languages are formal languages employed specifically to communicate instructions to computers or microprocessors for task execution. Through the years, object oriented programming has become one of many familiar and popular models designers and programmers utilize to implement functionality within computer systems. Object oriented programming is unique at least because it is premised on viewing programming in terms of objects or things rather than actions like other models.
The benefit of object technology arises out of three basic principles: encapsulation, polymorphism and inheritance. Objects hide or encapsulate the internal structure of their data and associated methods. Instead of exposing implementation details, objects present interfaces that represent their abstractions cleanly without extraneous information. Polymorphism takes encapsulation one-step further. Polymorphism allows the use of the same code for different data types—the idea being many shapes, one interface. Hence, a software component can make a request of another component without knowing exactly what that component is. The component that receives the request interprets it and figures out according to its variables and data how to execute the request. The third principle is inheritance, which enables developers to reuse pre-existing design and code. This capability allows developers to avoid creating all software from scratch. Rather, through inheritance, developers can derive subclasses that inherit and modify both state and behaviors of other classes.
The object oriented programming model is often defined via a class-based approach. In this system, objects are entities including both state and behavior. Both the state and behavior of an object are defined by a class, which identifies objects of a particular type. An object created based on a class definition is considered an instance of that class reflected in a dynamic type. Thus, a class specifies the data (i.e., state) that the object can contain as well as methods, functions, or behaviors that the object can perform. Methods operate to modify the internal state of the associated objects by altering the data contained therein. The combination of such data and methods in objects is often referred to as encapsulation in object-oriented programming. Encapsulation provides for the state of an object to be changed only by well-defined methods associated with the object. When the behavior of an object is confined to such well-defined locations and interfaces, changes (e.g., code modifications) in the object will have minimal impact on the other objects and elements in the system.
As mentioned briefly above, one of the most important features of object-oriented programming is inheritance. Inheritance describes a relationship between at least two classes. In particular, a class or subclass may be derived from another class (called a base class, parent class, etc.), where the subclass inherits the data attributes or state and methods of the base class. Stated differently, a class is inherited if it shares, modifies or extends another class state and behavior. Conventional class inheritance is typically employed for two purposes: (1) constraining a value set of a class by adding new fields and virtual methods and (2) adding methods allowing manipulation of an object's state in some convenient manner. These two needs are tightly related and are considered very dependent upon one another.